THE EFFECT OF THE POROUS STRUCTURE ON SORBENT SULFATION UNDER COAL-FIRED BOILER CONDITIONS

A study of the behavior of different sorbents (3 limestones, a commerc ial calcium carbonate and a commercial calcium hydroxide) in the sulfa tion process has been carried out in a drop-tube, using similar condit ions to those existing in sorbent injection in pulverized-coal boilers . The main variables affecting the sulfation process have been analyze d, namely, Ca/S molar ratio, SO2 concentration, temperature, sorbent p article size and reaction time. The work concentrates on the evolution of the porous system in the sorbents and its influence on their sulfa tion capacity. A direct relation between chemical structure (calcium h ydroxide-calcium carbonate) and sorbent reactivity was not found. Sorb ents with a widespread pore size distribution with pores above 100 Ang strom showed the highest reactivity and sulfation capacity, maintainin g pores of small size (under 80 Angstrom) at all times and operating c onditions. In the less reactive sorbents, pores less than 80 Angstrom became blocked during sulfation, being more sensitive to the effect of the different operating variables affecting the sulfation process.